How Quitting Afghanistan Presents Fresh Challenges For US

President Joe Biden's decision to withdraw foreign troops from Afghanistan ushers in a new set of risks for the United States and its military.

What are those risks, and how does the administration hope to mitigate them?

Does ' withdrawal' equal 'security vacuum'?

Officially, the Pentagon supports the US president's decision to end America's longest war. But many senior US commanders have been voicing their misgivings for months.

General Kenneth McKenzie, head of the US Central Command, recently told AFP that he had "reasons to believe" a withdrawal would allow the resurgence of extremist groups, with the risk of a collapse of the Afghan government.

CIA Director William Burns acknowledged on Wednesday that when the United States withdraws, the "US government's ability to collect and act on threats will diminish."

But he promised that the CIA would maintain "capabilities" in Afghanistan.

Retired General David Petraeus, who has operated in Iraq and Afghanistan, said Washington must be "really careful" with its rhetoric on the withdrawal.

"Ending US involvement in an endless war doesn't end the endless war. It just ends our involvement. And I fear that this war is going to get worse," he said.

Was it dangerous to announce a deadline?

The military had feared putting a date on the US departure, seeing it as a temptation to the Taliban, emboldened by what they see as a victory over the world's largest and most technologically-advanced army, to attack troops on the ground without consequences.

Biden has warned the Taliban against any such attempt, and Nato has said in a statement that "any Taliban attacks on Allied troops during this withdrawal will be met with a forceful response."

In addition, the allies were careful to say that the withdrawal would begin on May 1 -- the date by which it should have been completed under the Donald Trump administration's agreement with the Taliban.

But they also said it would be completed by September 11, the 20th anniversary of the attacks that prompted the invasion in the first place -- and a date already heralded by jihadists groups as a day of victory over the US.

"The chosen withdrawal date plays into the jihadi narrative of a 'crusader occupation' and seems like an error on the part of the Biden administration that could have been avoided," the Soufan Center said in an analysis.